A pump combiner and an erbium-doped fiber amplifier

Abstract

This application discloses a pump combiner and an erbium-doped fiber amplifier, which achieves coupling of pump light and signal light with a large mode field, improving coupling efficiency. The pump combiner includes a cladding structure, a first optical fiber, and a second optical fiber. The first optical fiber penetrates the cladding structure and extends from a first port and a second port. The first port is located on a first end face of the cladding structure, and the second port is located on a second end face of the cladding structure, with the first and second end faces parallel to each other. The area of ​​the first end face is larger than the area of ​​the second end face. The second optical fiber is connected to a third port, and the orientation of the third port is different from that of the first and second ports. The signal light propagates along the first optical fiber from the first port to the second port. The first pump light enters the cladding structure from the third port along the second optical fiber and, after reflection by a reflective surface, propagates towards the second port. The second port is used to output the coupled light of the first pump light and the signal light.

Description

Technical Field

[0001] This application relates to the field of optical communication, and more particularly to a pump combiner and an erbium-doped fiber amplifier. Background Technology

[0002] In recent years, with the rapid development of information and communication technologies, research on fiber optic amplifiers has further expanded gain bandwidth, propelling fiber optic communication systems towards high speed, large capacity, and long distance. As the demand for fiber optic capacity grows, space-division multiplexing wavelength-division transmission systems, represented by new types of optical fibers such as multi-core fibers and few-mode fibers, have gradually matured. In space-division multiplexing wavelength-division transmission systems, multiplexers are used to combine optical signals output from multiple signal transceiver units, and optical amplifiers are used to amplify the combined optical signals.

[0003] The aforementioned optical amplifier can specifically employ an erbium-doped fiber amplifier (EDFA). In an EDFA, the signal light and pump light are combined primarily through a pump combiner. The pump light provides energy to the system, enabling the combined light to be amplified through stimulated emission during transmission in the active fiber. Therefore, improving the coupling efficiency between the signal light and pump light is a crucial problem to be solved. Summary of the Invention

[0004] This application provides a pump combiner and an erbium-doped fiber amplifier, which realizes the coupling of pump light and signal light with a large mode field, improves the coupling efficiency, and avoids pump light loss caused by abrupt changes in the mode field area of ​​the pump light during the coupling process.

[0005] In a first aspect, this application provides a pump combiner. The pump combiner includes: a cladding structure, a first optical fiber, and a second optical fiber. The cladding structure includes a first port, a second port, and a third port. The first optical fiber penetrates the cladding structure and extends from both the first and second ports. The first port is disposed on a first end face of the cladding structure, and the second port is disposed on a second end face of the cladding structure. The first end face is parallel to the second end face, and the area of ​​the first end face is larger than that of the second end face. The second optical fiber is connected to the third port, and the orientation of the third port is different from the orientations of the first and second ports. A coupling region is included between the first and second end faces of the cladding structure. The longitudinal section of the coupling region gradually decreases in size from the first end face to the second end face, and the longitudinal section is parallel to both the first and second end faces.

[0006] Specifically, the signal light is transmitted from the first port to the second port along the first optical fiber, and the first pump light is input into the cladding structure from the third port along the second optical fiber and transmitted towards the second port after being reflected by the reflective surface. The second port is used to output the light coupled with the first pump light and the signal light.

[0007] In this embodiment, the first optical fiber used for transmitting signal light is wrapped by a cladding structure, which effectively enlarges the cladding diameter of the cladding structure to facilitate the input of pump light with a larger mode field. Furthermore, a coupling region is included between the first and second end faces of the cladding structure, and the longitudinal cross-section of this coupling region gradually decreases from the first end face to the second end face. As the pump light passes through the coupling region, its mode field area is gradually compressed to fit the first optical fiber, avoiding pump light loss caused by abrupt changes in the mode field area of ​​the pump light during coupling.

[0008] In some possible implementations, the mode field area of ​​the first pump light input from the third port is larger than the area of ​​the second end face. That is, the mode field area of ​​the first pump light is larger, and its mode field area will be compressed during the process of the first pump light passing through the coupling region, so that the signal light can couple with the pump light with a larger mode field, thereby improving the coupling efficiency.

[0009] In some possible implementations, the third port is disposed on the third end face of the cladding structure, perpendicular to the first end face, and located between the first end face and the coupling region. This approach provides a design position for the third port where, when the angle between the reflecting surface and the first optical fiber is 45°, the transmission direction of the pump light after reflection is the same as the transmission direction of the signal light, which helps improve coupling efficiency.

[0010] In some possible implementations, the pump combiner further includes a third optical fiber, and the cladding structure further includes a fourth port. The third optical fiber is connected to the fourth port, which is located on the fourth end face of the cladding structure. The fourth end face is parallel to the third end face and is located between the first end face and the coupling region. The second pump light enters the cladding structure from the fourth port along the third optical fiber and is reflected by the reflective surface before propagating towards the second port. The second port is specifically used to output the light resulting from the coupling of the first pump light, the second pump light, and the signal light. In this implementation, using multiple pump lights helps to increase the coupling efficiency between the pump light and the signal light.

[0011] In some possible implementations, the reflecting surface includes a first reflecting surface and a second reflecting surface, wherein the first reflecting surface reflects a first pump light and the second reflecting surface reflects a second pump light. The above method provides a specific implementation of the reflecting surface, increasing the practicality of this solution.

[0012] In some possible implementations, the reflective surface is the third end face of the cladding structure, which is perpendicular to the first end face and located between the first end face and the coupling region. In this implementation, a portion of the surface of the cladding structure is used as the reflective surface, eliminating the need for coating inside the cladding structure to form a reflective surface, thus reducing insertion loss and simplifying the fabrication of the cladding structure.

[0013] In some possible implementations, the cross-sectional shape of the covering structure consists of a rectangle and a trapezoid. The cross-section is perpendicular to the first end face, with one side of the rectangle corresponding to the first end face. The upper base of the trapezoid corresponds to the second end face, and the opposite side of one side of the rectangle forms the lower base of the trapezoid. This method provides a specific shape for the covering structure, which is relatively regular and easy to manufacture.

[0014] In some possible implementations, the angle between the side of the trapezoid and the first optical fiber is acute, which results in a high coupling efficiency between the signal light and the pump light.

[0015] In some possible implementations, the second end face is circular, and its diameter is the same as the diameter of the inner cladding of the first optical fiber. It should be understood that if the diameter of the second end face is larger than the diameter of the inner cladding of the first optical fiber, some pump light will not be able to couple with the signal light transmitted in the first optical fiber. Therefore, this design can improve the coupling efficiency between the signal light and the pump light.

[0016] In some possible implementations, the first optical fiber is a multi-core optical fiber, that is, multiplexing is achieved through spatial division multiplexing, which can overcome the Shannon capacity limitation of optical fiber transmission and achieve the purpose of expanding the capacity of the transmission system.

[0017] In some possible implementations, the second optical fiber is a multimode fiber, which reduces implementation costs.

[0018] In some possible implementations, the pump combiner provided in this application employs an all-fiber structure. For example, if both the first and second optical fibers are made of glass, then the cladding structure can also be made of glass, which facilitates fabrication.

[0019] In some possible implementations, a reflective film is provided on the reflective surface to reflect pump light of a specified wavelength, which improves the feasibility of this solution.

[0020] In some possible implementations, the wavelength of the signal light is longer than that of the first pump light, which improves practicality.

[0021] In some possible implementations, the cladding structure is connected to the first and second optical fibers respectively by fusion splicing, making the overall structure of the pump combiner more stable.

[0022] Secondly, this application provides an erbium-doped fiber amplifier. The erbium-doped fiber amplifier includes: an erbium-doped fiber, a pump beam splitter, and a pump beam combiner as described in any embodiment of the first aspect. The pump beam combiner and the pump beam splitter are connected via the erbium-doped fiber. The pump beam combiner outputs a signal light coupled to the pump light into the erbium-doped fiber. The coupled light is amplified in the erbium-doped fiber and transmitted to the pump beam splitter. The pump beam splitter filters out the pump light and outputs the amplified signal light.

[0023] In this embodiment, the first optical fiber used for transmitting signal light is wrapped by a cladding structure, which effectively increases the cladding diameter of the cladding structure to facilitate the input of pump light with a larger mode field into the cladding structure. Furthermore, a coupling region is included between the first and second end faces of the cladding structure, and the longitudinal cross-section of this coupling region gradually decreases from the first end face to the second end face. As the pump light passes through the coupling region, its mode field area is gradually compressed to fit the first optical fiber, thereby achieving coupling between the pump light with a larger mode field and the signal light, improving coupling efficiency, and avoiding pump light loss caused by abrupt changes in the mode field area of ​​the pump light during coupling. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a multi-core wavelength division transmission system in an embodiment of this application;

[0025] Figure 2 This is a schematic diagram of a structure of an erbium-doped fiber amplifier in an embodiment of this application;

[0026] Figure 3 This is a schematic diagram of the first structure of the pump combiner in the embodiments of this application;

[0027] Figure 4(a) is a schematic cross-sectional view of a pump combiner in an embodiment of this application;

[0028] Figure 4(b) shows two cross-sectional schematic diagrams of the pump combiner in the embodiments of this application;

[0029] Figure 4(c) is a schematic diagram of three cross-sections of the pump combiner in the embodiments of this application;

[0030] Figure 5 This is a schematic diagram illustrating the change in coupling efficiency between the signal light and the pump light in an embodiment of this application.

[0031] Figure 6 This is a schematic longitudinal section of the pump combiner in an embodiment of this application;

[0032] Figure 7 This is a schematic diagram of the first fabrication process of the pump combiner in the embodiments of this application;

[0033] Figure 8 This is a schematic diagram of a second structure of the pump combiner in an embodiment of this application;

[0034] Figure 9 This is a schematic diagram of a third structure of the pump combiner in the embodiments of this application;

[0035] Figure 10 This is a schematic diagram of the fourth structure of the pump combiner in the embodiments of this application. Detailed Implementation

[0036] This application provides a pump combiner and an erbium-doped fiber amplifier, which achieves coupling of pump light with a large mode field to signal light, improves coupling efficiency, and avoids pump light loss caused by abrupt changes in the mode field area of ​​the pump light during coupling. The terms "first," "second," "third," etc. (if present) in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments described herein can be implemented in a sequence other than that illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0037] The pump combiner provided in this application is mainly used in erbium-doped fiber amplifiers (EDFAs). EDFAs are used in optical networks to amplify optical signals so that they can be received. With the increasing demand for fiber optic capacity, space-division multiplexing wavelength-division transmission systems, represented by new types of fibers such as multi-core fibers and few-mode fibers, are gradually maturing. The following section introduces an application scenario of erbium-doped fiber amplifiers using a multi-core wavelength-division transmission system as an example.

[0038] Figure 1 This is a schematic diagram of a multi-core wavelength division multiplexing (WDM) transmission system according to an embodiment of this application. Figure 1 As shown, multiple transceiver units can output optical signals of different wavelengths. A multiplexer combines the input optical signals of different wavelengths and outputs the combined multi-wavelength signal. The multi-wavelength signal can be transmitted via a multi-core fiber (MCF), which provides multiple spatially parallel channels. An EDFA is used to amplify the multi-wavelength signal. An optical add-drop multiplexer (OADM) is used to add or drop the multi-wavelength signal. A demultiplexer is used to demultiplex the input multi-wavelength signal and output the different wavelengths of optical signals to different transceiver units.

[0039] Figure 2 This is a schematic diagram of one structure of an erbium-doped fiber amplifier in an embodiment of this application. Figure 2As shown, the erbium-doped fiber amplifier includes a pump combiner, a pump splitter, and erbium-doped fiber. The pump combiner and pump splitter are connected via the erbium-doped fiber. The two input ports of the pump combiner receive the signal light and the pump light, respectively, and the pump combiner couples the signal light and the pump light for output. The coupled light propagates in the erbium-doped fiber and is amplified based on stimulated emission. The pump splitter filters out the pump light and outputs the amplified signal light.

[0040] The pump combiner provided in the embodiments of this application will be described in detail below.

[0041] Figure 3 This is a schematic diagram of the first structure of the pump combiner in an embodiment of this application. Figure 3 As shown, the pump combiner includes a first optical fiber 10, a second optical fiber 20, and a cladding structure 30. The cladding structure 30 includes ports 1, 2, and 3. Port 1 is located on a first end face 301 of the cladding structure 30, and port 2 is located on a second end face 302. The first end face 301 and the second end face 302 are parallel, and the area of ​​the first end face 301 is larger than the area of ​​the second end face 302. The first optical fiber 10 passes through the cladding structure 30 and extends from ports 1 and 2 respectively; that is, a section of the first optical fiber 10 is wrapped by the cladding structure 30. The first optical fiber 10 is used to transmit signal light, which is transmitted along the first optical fiber 10 from port 1 to port 2. The second optical fiber 20 is connected to port 3 of the cladding structure 30, and the orientation of port 3 is different from the orientation of ports 1 and 2. The second optical fiber 20 is used to transmit pump light; that is, the direction in which the pump light enters the cladding structure 30 is different from the direction in which the signal light enters the cladding structure 30. The cladding structure 30 also includes a reflective surface 40. After the pump light enters the cladding structure 30 from port 3 along the second optical fiber 20, it will be reflected by the reflective surface 40 and transmitted towards port 2. Port 2 will output the light resulting from the coupling of the signal light and the pump light.

[0042] It should be noted that a coupling region 305 is included between the first end face 301 and the second end face 302 of the covering structure 30. It should be understood that since the area of ​​the first end face 301 is larger than the area of ​​the second end face 302, the longitudinal section of the covering structure 30 necessarily tends to decrease from the first end face 301 to the second end face 302, where this longitudinal section is a plane parallel to the first end face 301 and the second end face 302. Specifically, the longitudinal section of the coupling region 305 gradually decreases from the first end face 301 to the second end face 302. That is to say, the longitudinal section of the covering structure 30 does not suddenly decrease at a certain position, but gradually decreases through a transition region, which is the coupling region 305. Figure 3 For example, the coupling region 305 can be an approximately frustum-shaped structure.

[0043] In some possible implementations, the mode field area of ​​the pump light input from port 3 is larger than the area of ​​the second end face 302. Therefore, after the pump light is reflected by the reflecting surface 40 and propagates in the coupling region 305, the mode field area of ​​the pump light will gradually decrease to match the size of the second end face 302, avoiding pump light loss caused by abrupt changes in the mode field area of ​​the pump light during coupling. This allows the signal light to be efficiently coupled with the large mode field pump light.

[0044] Figure 4(a) is a schematic cross-sectional view of a pump combiner in an embodiment of this application. As shown in Figure 4(a), the cross-sectional shape of the covering structure 30 is composed of a rectangle and a trapezoid, wherein the cross-section is perpendicular to the first end face 301. Side a of the rectangle corresponds to the first end face 301. Side b of the rectangle is opposite to side a, and side b of the rectangle is also the lower base of the trapezoid. The upper base c of the trapezoid corresponds to the second end face 302. Figure 3 As shown in Figure 4(a), the rectangular cross-section corresponds to a segment of the approximately cylindrical structure 30. The trapezoidal cross-section corresponds to a segment of the approximately frustum-shaped structure 30, i.e., the coupling region 305. When the pump light propagates in the approximately frustum-shaped structure, its mode field area gradually decreases.

[0045] It should be noted that changing the angle θ between the side of the trapezoid and the first optical fiber 10 will also change the coupling efficiency between the pump light and the signal light. Specifically, both excessively large and small θ will result in significant pump light loss. Figure 5 This is a schematic diagram illustrating the change in coupling efficiency between the signal light and pump light in an embodiment of this application. For example... Figure 5 As shown, the horizontal axis represents the angle θ between the side of the trapezoid and the first optical fiber 10, and the vertical axis represents the coupling efficiency between the signal light and the pump light. It can be seen that the coupling efficiency between the signal light and the pump light is highest when θ is in the range of 23.7°-27.6°. It should be understood that the range of θ provided above is only an example; in practical applications, other ranges can be used, such as θ being an acute angle, etc., but this is not specifically limited here.

[0046] It should be noted that, in practical applications, the shape of the coupling region in the covering structure includes, but is not limited to, the shapes described above. Figure 3 The example is shown in Figure 4(a). Figure 4(b) is a schematic diagram of two cross-sections of the pump combiner in an embodiment of this application. Figure 4(c) is a schematic diagram of three cross-sections of the pump combiner in an embodiment of this application. As shown in Figures 4(b) and 4(c), the cross-section of the coupling region does not have to be a regular trapezoid, as long as the longitudinal section of the coupling region gradually decreases.

[0047] In one possible implementation, the second end face 302 is circular, and its diameter is the same as the diameter of the inner cladding of the first optical fiber 10. That is, port 2 occupies the entire second end face 302, and its size is precisely matched to the size of the inner cladding of the first optical fiber 10. It should be understood that if the diameter of the second end face 302 is larger than the diameter of the inner cladding of the first optical fiber 10, some pump light will not be able to couple with the signal light transmitted in the first optical fiber 10. Therefore, this design can improve the coupling efficiency between the signal light and the pump light.

[0048] In one possible implementation, the first optical fiber 10 can be a multi-core optical fiber. A multi-core optical fiber constructs multiple parallel spatial channels through multiple cores within a single optical fiber, achieving multiplexed transmission through spatial division multiplexing. This overcomes the Shannon capacity limitation of optical fiber transmission, thereby expanding the transmission system capacity. It should be understood that different numbers of cores and different core arrangements can be used in different application scenarios; no specific limitations are made here. The second optical fiber 20 can be a multimode optical fiber, resulting in lower costs.

[0049] In one possible implementation, the wavelength of the signal light is greater than the wavelength of the pump light. For example, the wavelength range of the signal light could be 1470nm-1620nm, and the wavelength range of the pump light could be 970nm-1420nm. A reflective film is disposed on the reflective surface 40, which can reflect the pump light and transmit the signal light.

[0050] In one possible implementation, the pump combiner provided in this application adopts an all-fiber structure. For example, if both the first fiber 10 and the second fiber 20 are made of glass, then the cladding structure 30 is also made of glass, which facilitates processing. Furthermore, the cladding structure 30 can be connected to the first fiber 10 and the second fiber 20 respectively by fusion splicing, making the overall structure of the pump combiner more stable.

[0051] It should be noted that the pump combiner can have one or more ports for inputting pump light. Furthermore, the input position of the pump light on the pump combiner can be varied. Several specific implementation methods are provided below.

[0052] like Figure 3 As shown, port 3 is disposed on the third end face 303 of the cladding structure 30. The third end face 303 is perpendicular to the first end face 301, and the direction of the first optical fiber 10 is perpendicular to the direction of the second optical fiber 20. Furthermore, the third end face 303 is located between the first end face 301 and the coupling region 305, in conjunction with the above... Figures 4(a)-4(c)It is known that the cross-section of port 3 is within a rectangular area. By placing port 3 on the third end face 303, the second optical fiber 20 can be better fitted to the cladding structure 30. Preferably, the angle between the reflecting surface 40 and the first optical fiber 10 is 45°, and the transmission direction of the pump light after reflection by the reflecting surface 40 is the same as the transmission direction of the signal light, which helps to improve the coupling efficiency.

[0053] It should be understood that this application does not limit the specific dimensions of the first optical fiber 10, the second optical fiber 20, and the cladding structure 30. As an example, the outer cladding diameter of the first optical fiber 10 and the second optical fiber 20 is 125 μm, the inner cladding diameter of the first optical fiber 10 is 80 μm, and the inner cladding diameter of the second optical fiber 20 is 105 μm. Figure 6 This is a schematic longitudinal section of the pump combiner in an embodiment of this application. Figure 6 As shown, L represents the diameter of the second optical fiber 20, d represents the inner cladding radius of the first optical fiber 10, and R represents the radius of the first end face 301 on the cladding structure 30. Assume r = L / 2 = 62.5 μm and d = 40 μm. In other words, the diameter of the first end face 301 is at least 150um. Considering the manufacturing process, the first end face 301 can be set to 300um-500um.

[0054] The following is about Figure 3 The fabrication process of the pump combiner shown is described.

[0055] Figure 7 This is a schematic diagram of the first fabrication process of the pump combiner in this embodiment of the application. Figure 7 As shown, the first step is to cut the multi-core optical fiber into two segments and coat the cut beveled surface with a reflective coating to form a reflective surface. The second step is to fix the two ends of the cut optical fiber with clamps and adjust the position of the two segments to splice them together with their cores aligned. After splicing, the entire structure is wrapped with low-refractive-index UV adhesive, and after curing, a complete and stable cylindrical structure is obtained. The third step is to clamp one end of the cylinder with a clamp and rotate and grind the other end, creating a frustum without changing the core structure to form a coupling zone. The fourth step is to grind a platform on the side of the entire structure, i.e., the third end face 303, thus completing the processing of the cladding structure. The size of this platform needs to accommodate the insertion of the second optical fiber. The fifth step is to fuse the signal light input ends and the combined light output ends on the left and right sides using an asymmetric fusion splicer, and apply low-refractive-index UV adhesive around the fusion joint using a dotting method and allow it to cure. For the pump light input at the top, a precision motor is used to make the second optical fiber fit tightly against the side platform, while the entire structure is immersed in low-refractive-index UV adhesive and cured to obtain a stable overall structure.

[0056] Figure 8This is a schematic diagram of a second structure of the pump combiner in an embodiment of this application. For example... Figure 8 As shown, it differs from the above. Figure 3 The pump combiner shown in this embodiment further includes a third optical fiber 50, and the cladding structure 30 further includes a port 4. The third optical fiber 50 is connected to the port 4, which is located on the fourth end face 304 of the cladding structure 30. The fourth end face 304 is parallel to the third end face 303. The direction of the first optical fiber 10 is perpendicular to the direction of the third optical fiber 50. Furthermore, both the third end face 303 and the fourth end face 304 are located between the first end face 301 and the coupling region 305. (This is in conjunction with the above...) Figures 4(a)-4(c) It is known that the cross-sections of ports 3 and 4 are both within a rectangular range. The reflecting surface 40 can be divided into reflecting surface 401 and reflecting surface 402. Reflecting surface 401 reflects the pump light input along the second optical fiber 20, and reflecting surface 402 reflects the pump light input along the third optical fiber 50. After reflection, both pump lights will output towards port 2, and after coupling with the signal light, they will output from port 2. By using multiple pump lights in this way, the coupling efficiency between the pump light and the signal light can be increased. Preferably, the angle between reflecting surface 401 and the first optical fiber 10 is 45°, the angle between reflecting surface 402 and the first optical fiber 10 is 45°, and the angle between reflecting surface 401 and reflecting surface 402 is 90°. The transmission direction of the two pump lights after reflection is the same as the transmission direction of the signal light, which helps to improve the coupling efficiency.

[0057] The following is about Figure 8 The fabrication process of the pump combiner shown is described.

[0058] Step 1: Cut the multi-core optical fiber into two segments. One segment has two convex end faces at a 90° angle, while the other segment has two concave end faces at a 90° angle. Reflective coatings can be deposited on the two beveled surfaces to form reflective surfaces. Step 2: Fix the two ends of the cut optical fiber with clamps and adjust their positions to splice them together with their cores aligned. After splicing, wrap the entire structure with low-refractive-index UV adhesive. After curing, a complete and stable cylindrical structure is obtained. Step 3: Clamp one end of the cylinder and rotate and grind the other end, creating a frustum without altering the core structure to form a coupling zone. Step 4: Grind a platform on each of the two sides of the entire structure, namely the third end face 303 and the fourth end face 304. This completes the processing of the cladding structure. The size of one platform needs to accommodate the insertion of the second optical fiber, and the size of the other platform needs to accommodate the insertion of the third optical fiber. Step 5: For the signal light input terminals and beam combiner output terminals on the left and right sides, use an asymmetric fusion splicing method to fuse them. Apply low-refractive-index UV adhesive around the fusion joint and allow it to cure. For the pump light input terminals at the top and bottom, use precision motors to firmly attach the second and third optical fibers to the two side platforms respectively. Simultaneously, immerse the entire structure in low-refractive-index UV adhesive and allow it to cure to obtain a stable overall structure.

[0059] Figure 9 This is a schematic diagram of a third structure of the pump combiner in an embodiment of this application. For example... Figure 9 As shown, it differs from the above. Figure 3 and Figure 8 In the pump combiner shown in this embodiment, the third end face 303 on the cladding structure 30 is a reflective surface. The third end face 303 is located between the first end face 301 and the coupling region 305, and the port 3 is located on the arc surface opposite the third end face 303. Specifically, the pump light input from the port 3 along the second optical fiber 20 will be reflected by the third end face 303 and transmitted towards the port 2. It should be understood that the input direction of the pump light is at an acute angle to the input direction of the signal light. With the above method, it may not be possible to guarantee that all pump light can be transmitted to the port 2 after reflection, sacrificing some coupling efficiency. However, in this embodiment, a portion of the surface of the cladding structure is used as a reflective surface, eliminating the need for coating inside the cladding structure to form a reflective surface, reducing insertion loss, and also reducing the manufacturing difficulty of the cladding structure.

[0060] The following is about Figure 9 The fabrication process of the pump combiner shown is described.

[0061] Step 1: Grind a platform, i.e., the third end face 303, on the side of the multi-core optical fiber. Optionally, a reflective film can be deposited on the inner side of the third end face 303. Step 2: Clamp one end of the multi-core optical fiber with a fixture, and rotate and grind the other end to create a frustum without altering the fiber core structure, thus forming a coupling region. Step 3: For the signal light input ends and the combined light output ends on both sides, use an asymmetric fusion splicer to fusion splice them. Apply low-refractive-index UV adhesive around the splice and allow it to cure. For the pump light input end, use a precision motor to press the second optical fiber tightly against the arc surface opposite the platform, ensuring the pump light input direction forms an acute angle with the signal light input direction. Simultaneously, immerse the entire structure in low-refractive-index UV adhesive and allow it to cure to obtain a stable overall structure.

[0062] Figure 10 This is a schematic diagram of a fourth structure of the pump combiner in this application embodiment. For example... Figure 10 As shown, it differs from the above. Figure 9 In the pump combiner shown in this embodiment, the third end face 303 of the covering structure 30 may not be ground, meaning that one section of the covering structure 30 can maintain a cylindrical structure. Port 3 is located on the arc surface of the cylindrical structure, and the pump light input from port 3 is reflected by the arc surface opposite port 3 to port 2. The input direction of the pump light forms an acute angle with the input direction of the signal light. Apart from the above differences, this embodiment is similar to the one described above. Figure 9 The fabrication process for the pump combiner shown is similar and will not be repeated here. It should be understood that... Figure 9 The embodiment shown has a polished reflective surface, resulting in better reflection of pump light. Figure 10 The embodiment shown does not require additional polishing of the reflective surface, making the preparation process simpler.

[0063] As can be seen from the above embodiments, the first optical fiber used for transmitting signal light is wrapped by a cladding structure, which is equivalent to increasing the cladding diameter of the cladding structure to facilitate the input of pump light with a larger mode field into the cladding structure. Furthermore, a coupling region is included between the first and second end faces of the cladding structure, and the longitudinal cross-section of this coupling region gradually decreases from the first end face to the second end face. As the pump light passes through the coupling region, its mode field area is gradually compressed to fit the first optical fiber, thereby achieving coupling between the pump light with a larger mode field and the signal light, improving coupling efficiency, and avoiding pump light loss caused by abrupt changes in the mode field area of ​​the pump light during coupling.

[0064] It should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit it. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A pump-driven bundle combiner, characterized in that, include: The cladding structure comprises a first optical fiber, a second optical fiber, and a third optical fiber. The cladding structure includes a first port, a second port, and a third port. The first optical fiber penetrates the cladding structure and extends from both the first port and the second port. The first port is disposed on a first end face of the cladding structure, and the second port is disposed on a second end face of the cladding structure. The first end face is parallel to the second end face, and the area of ​​the first end face is larger than that of the second end face. The second optical fiber is connected to the third port, and the orientation of the third port is different from that of both the first and second ports. A coupling region is included between the first and second end faces of the cladding structure. The longitudinal section of the coupling region gradually decreases in size from the first end face to the second end face, and the longitudinal section is parallel to both the first and second end faces. The signal light is transmitted from the first port to the second port along the first optical fiber. The first pump light is input into the cladding structure from the third port along the second optical fiber and is transmitted toward the second port after being reflected by the reflective surface. The second port is used to output the light coupled with the first pump light and the signal light.

2. The pump combiner according to claim 1, characterized in that, The mode field area of ​​the first pump light input from the third port is greater than the area of ​​the second end face.

3. The pump combiner according to claim 1, characterized in that, The third port is disposed on the third end face of the covering structure, the third end face is perpendicular to the first end face, and the third end face is located between the first end face and the coupling area.

4. The pump combiner according to claim 3, characterized in that, The pump combiner further includes a third optical fiber, and the cladding structure further includes a fourth port. The third optical fiber is connected to the fourth port. The fourth port is disposed on the fourth end face of the cladding structure. The fourth end face is parallel to the third end face and is located between the first end face and the coupling region. The second pump light is input into the cladding structure from the fourth port along the third optical fiber and is transmitted toward the second port after being reflected by the reflective surface. The second port is specifically used to output the light after the first pump light, the second pump light and the signal light are coupled.

5. The pump combiner according to claim 4, characterized in that, The reflective surface includes a first reflective surface and a second reflective surface, wherein the first reflective surface is used to reflect a first pump light and the second reflective surface is used to reflect a second pump light.

6. The pump combiner according to claim 1, characterized in that, The reflective surface is the third end face of the covering structure, the third end face is perpendicular to the first end face, and the third end face is located between the first end face and the coupling area.

7. The pump combiner according to any one of claims 1 to 6, characterized in that, The cross-sectional shape of the covering structure is composed of a rectangle and a trapezoid. The cross-section is perpendicular to the first end face. One side of the rectangle corresponds to the first end face, the upper base of the trapezoid corresponds to the second end face, and the opposite side of one side of the rectangle is the lower base of the trapezoid.

8. The pump combiner according to claim 7, characterized in that, The angle between the side of the trapezoid and the first optical fiber is an acute angle.

9. The pump combiner according to any one of claims 1 to 6, characterized in that, The second end face is circular, and the diameter of the second end face is the same as the diameter of the inner cladding of the first optical fiber.

10. The pump combiner according to any one of claims 1 to 6, characterized in that, The first optical fiber is a multi-core optical fiber.

11. The pump combiner according to any one of claims 1 to 6, characterized in that, The second optical fiber is a multimode optical fiber.

12. The pump combiner according to any one of claims 1 to 6, characterized in that, The material of the covering structure is glass.

13. The pump combiner according to any one of claims 1 to 6, characterized in that, A reflective film is provided on the reflective surface.

14. The pump combiner according to any one of claims 1 to 6, characterized in that, The wavelength of the signal light is greater than the wavelength of the first pump light.

15. The pump combiner according to any one of claims 1 to 6, characterized in that, The cladding structure is connected to the first optical fiber and the second optical fiber respectively by fusion splicing.

16. An erbium-doped fiber amplifier, characterized in that, include: Erbium-doped fiber, a pump splitter, and a pump combiner as described in any one of claims 1 to 15, wherein the pump combiner and the pump splitter are connected via the erbium-doped fiber; The pump combiner is used to output signal light coupled with pump light to the erbium-doped fiber. The coupled light is amplified in the erbium-doped fiber and transmitted to the pump splitter. The pump splitter is used to filter out the pump light and output the amplified signal light.

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